Preparation And Properties Of ?-diketone Based Rare Earth Magneto-optical Bifunctional Molecular Materials

In recent years,the design,preparation and application of multifunctional materials have become a research hotspot.Rare earth complexes are promising magneto-optical multifunctional materials thanks to the excellent magnetic and optical properties of rare earth ions.The?-diketone ligand has a good coordination ability,and the coordination with rare earth ions can not only sensitize the luminescence but also affect the magnetic properties.Therefore,in this paper,rare earth magneto-optical bifunctional molecular materials are designed and synthesized by using?-diketone ligand as the main ligand and different auxiliary ligands.1.Two isostructural mononuclear sulfur-based rare earth complexes,[(dbm)₂Er(dtc)(phen)](1-Er)and[(dbm)₂Tb(dtc)(phen)](1-Tb)(dtc^-=diethyldithiocarbamate anion,phen=1,10-phenanthroline)were synthesized based on dibenzoylmethane(Hdbm).Magnetism and luminescence measurements show that 1-Er is a field-induced single-molecule magnet and exhibits the characteristic emission peaks of Er³⁺ion in the visible and near-infrared regions.Therefore,1-Er is a sulfur-based rare earth magneto-optical bifunctional molecular material.2.Two types of mononuclear rare earth complexes[(dbm)₃Ln(dmbipy)](2-Ln,Ln=Eu,Tb,Dy,Ho,Er,Tm,and Yb)and[(dbm)₂Ln(dmobipy)(NO₃)](3-Ln,Ln=Dy,Ho,and Er)(dmbipy=4,4'-dimethyl-2,2'-bipyridine,dmobipy=4,4'-dimethoxy-2,2'-bipyridine)have been synthesized with dibenzoylmethane as the main ligand and by tuning the substituents at 4,4'-positions of 2,2'-bipyridine.Molecular formula,geometric structure,magnetic and luminescence properties of the complexes are significantly modified by replacing the auxiliary ligands substituent from–CH₃(dmbipy)to–OCH₃(dmobipy).Research shows that 2-Dy is a single-molecule magnet with an effective energy barrier of 271 K,which is the highest of[(dbm)₃Dy L](L=auxiliary ligands)type single-molecule magnets,but no characteristic emission peaks of Dy³⁺ions were observed;2-Er,3-Dy and 3-Er are field-induced single-molecule magnets with an effective energy barrier of 9 K,41 K and 26 K,respectively,and can exhibit characteristic emissions of Er³⁺/Dy³⁺ions.Therefore,2-Dy is a rare earth magnetic molecular material,while 2-Er,3-Dy and 3-Er are rare earth magneto-optical bifunctional molecular materials.In addition,2-Eu,2-Tb,2-Ho,2-Tm,2-Yb and 3-Ho are all luminescent molecular materials.3.Two kinds of mononuclear rare earth complexes[(tfnb)₃Ln(dmbipy)](4-Ln,Ln=Tb,Dy and Ho)and[(tfnb)₃Ln(phen)](5-Ln,Ln=Tb and Dy)were synthesized based on4,4,4-trifluoro-1-(2-naphthyl)-1,3-butanedione(Htfnb)and different auxiliary ligands(dmbipy or phen).Structure analysis shows that 4-Dy and 5-Dy are octacoordinated by six O atoms of three tfnb^-ligands and two N atoms of one dmbipy or phen ligand.The results show that 4-Dy and 5-Dy are two single-molecule magnets with the effective energy barriers of 139 K and 193 K.Comapred to 4-Dy,5-Dy is closer to the ideal D_2d coordination configuration,yeilding superior magnetic properties.Therefore,4-Dy and 5-Dy are two examples of rare earth magnetic molecular materials...